However, I can't figure out how to highlight the polygon even though I know which one it is. I have previously defined a style for when the mouse hovers over the polygon and it is selected, but I don't know how to apply this style to the chosen polygon.

Thanks @GlennPlas - that link pointed out that selection can be done using selectFeature.select(this.vlayer.features[i]); when selectFeature is defined as a control. Not sure if you can move your comment to answer, but I could mark as the answer if so.
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djqNov 12 '12 at 22:30

It will be a short answer, but It's good to be able to close a question, GIS has a lower answer rate than SO.
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Glenn PlasNov 13 '12 at 7:56